1. Field of the Invention
The present invention relates to a ring network comprised of a plurality of transmission apparatuses (nodes) connected via a ring-shaped transmission line and switching from a state operating under a uni-directional path switched ring (UPSR) mode to a bi-directional line switched ring (BLSR) mode by interchanging paths and to a method for path interchange therein.
2. Description of the Related Art
As will be explained in more detail with reference to the drawings later, for switching from the UPSR mode to the BLSR mode in a ring network, it is known to provide a transmission apparatus with a switch for switching between a function unit conforming to the UPSR mode and a function unit conforming to the BLSR mode and operate the switch etc. or to replace a protection side function unit of the UPSR mode with a protection side function unit of the BLSR mode, operate the protection side as the working side, and, during the operation, replace the working side function unit. Since excess mechanisms have to be added or the function units have to be replaced and then reconnected, the amount of work becomes greater and the time required for switching becomes longer.
Therefore, it may be considered to switch from the UPSR mode to the BLSR mode by a higher order operating system (Ops). In this case, however, an operator has to be present and change paths while determining the conditions of each path. The processing time therefore becomes extremely long. Further, it is not possible to deal with faults occurring in the process of path interchange processing.